black belt

Short definition from Wiktionary

Noun

1. 1
   The highest belt colour in various martial arts.
2. 2
   Someone who has attained the black belt in martial arts.
3. 3
   Great skill in any field.
4. 4
   A senior manager who is expert in one of various management systems such as Six Sigma or DMAIC and acts in a project leader or mentor role.
5. 5
   A geographic region where the residents are predominantly or exclusively African-American.
6. 6
   A roughly crescent-shaped geological formation of dark fertile soil in the Southern United States.
7. 7
   Alternative letter-case form of black belt.